Market forces demand that image sensors continue to have ever increasing frame rates and improved gain performance. Accordingly, the analog gain block of modern image sensors, including a differential amplifier, analog-to-digital converter (ADC), etc., is often designed to operate faster and more linearly, leading to greater power consumption. For example, the power consumed by image sensors in the current generation can be greater than twice the power consumed by those in the previous generation. Greater power consumption results in a higher operating temperature for the image sensor. Experimental data shows that a junction temperature of a typical modern image sensor is approximately 30-40° Celsius higher than its ambient temperature, depending on the package module size, material, etc. Consequently, temperature dependence of the image sensor bias has become a significant issue in image sensor design.
Current reference modules are often employed to bias components, such as the analog gain block, of modern image sensors. However, conventional current reference modules typically provide reference currents having positive temperature coefficients, meaning that an increase of temperature leads to a greater reference current value. A greater reference current value causes a greater power consumption, resulting in a higher operating temperature for the image sensor.
Thus, systems and methods for providing a reference current with a negative temperature coefficient are needed to address self-heating issues associated with conventional current reference modules.
In the drawings, like reference numbers indicate identical or functionally similar elements. Additionally, the leftmost digit(s) of a reference number identifies the drawing in which the reference number first appears.